From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E6EDC25B06 for ; Sun, 14 Aug 2022 16:43:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242793AbiHNQnb (ORCPT ); Sun, 14 Aug 2022 12:43:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243346AbiHNQku (ORCPT ); Sun, 14 Aug 2022 12:40:50 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B699865D5; Sun, 14 Aug 2022 09:31:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7053EB80B37; Sun, 14 Aug 2022 16:30:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6392EC433D7; Sun, 14 Aug 2022 16:30:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660494658; bh=iS9yqPrrykOoJinZudE3RI49uScGLU+2ThjG/LbrXTs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LD06aie8VPTm1xhhtvEzzMwJOI3kod/sdbTyUagUV6iUMEqfyP+2Bml3ZPdZ5lxEV FJH9Az3/LC+V67IoP0q0RWX2yC+32poZ7uCiFjPFTsnwkSIWy5wA3O3e7MzQkC00vv XSNz25St4TSxLd8C6nBdD5rawdr69wOdaIp69w2LYc8vIaTs3q9lqiqDWg1W/MiRp6 MgLqF+prUgK+BxdksPrWHnEEV7xVA56EVu8csc5G8KJzGNS4Y0Ve2Tt5rGOmokO9lR EHFRAnYWWL381YzXzdoP3MXxgPrkowmZkZN/7b2epjPoCVeDYe9mz2ZWD83+L4FawB nEli0lswEzsKA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Takashi Iwai , Sasha Levin , perex@perex.cz, tiwai@suse.com, alsa-devel@alsa-project.org Subject: [PATCH AUTOSEL 4.9 4/8] ALSA: core: Add async signal helpers Date: Sun, 14 Aug 2022 12:30:37 -0400 Message-Id: <20220814163041.2399552-4-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220814163041.2399552-1-sashal@kernel.org> References: <20220814163041.2399552-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takashi Iwai [ Upstream commit ef34a0ae7a2654bc9e58675e36898217fb2799d8 ] Currently the call of kill_fasync() from an interrupt handler might lead to potential spin deadlocks, as spotted by syzkaller. Unfortunately, it's not so trivial to fix this lock chain as it's involved with the tasklist_lock that is touched in allover places. As a temporary workaround, this patch provides the way to defer the async signal notification in a work. The new helper functions, snd_fasync_helper() and snd_kill_faync() are replacements for fasync_helper() and kill_fasync(), respectively. In addition, snd_fasync_free() needs to be called at the destructor of the relevant file object. Link: https://lore.kernel.org/r/20220728125945.29533-2-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- include/sound/core.h | 8 ++++ sound/core/misc.c | 94 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+) diff --git a/include/sound/core.h b/include/sound/core.h index 31079ea5e484..d5d0e5e53920 100644 --- a/include/sound/core.h +++ b/include/sound/core.h @@ -457,4 +457,12 @@ snd_pci_quirk_lookup_id(u16 vendor, u16 device, } #endif +/* async signal helpers */ +struct snd_fasync; + +int snd_fasync_helper(int fd, struct file *file, int on, + struct snd_fasync **fasyncp); +void snd_kill_fasync(struct snd_fasync *fasync, int signal, int poll); +void snd_fasync_free(struct snd_fasync *fasync); + #endif /* __SOUND_CORE_H */ diff --git a/sound/core/misc.c b/sound/core/misc.c index f2e8226c88fb..efe26b8ca57f 100644 --- a/sound/core/misc.c +++ b/sound/core/misc.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #ifdef CONFIG_SND_DEBUG @@ -153,3 +154,96 @@ snd_pci_quirk_lookup(struct pci_dev *pci, const struct snd_pci_quirk *list) } EXPORT_SYMBOL(snd_pci_quirk_lookup); #endif + +/* + * Deferred async signal helpers + * + * Below are a few helper functions to wrap the async signal handling + * in the deferred work. The main purpose is to avoid the messy deadlock + * around tasklist_lock and co at the kill_fasync() invocation. + * fasync_helper() and kill_fasync() are replaced with snd_fasync_helper() + * and snd_kill_fasync(), respectively. In addition, snd_fasync_free() has + * to be called at releasing the relevant file object. + */ +struct snd_fasync { + struct fasync_struct *fasync; + int signal; + int poll; + int on; + struct list_head list; +}; + +static DEFINE_SPINLOCK(snd_fasync_lock); +static LIST_HEAD(snd_fasync_list); + +static void snd_fasync_work_fn(struct work_struct *work) +{ + struct snd_fasync *fasync; + + spin_lock_irq(&snd_fasync_lock); + while (!list_empty(&snd_fasync_list)) { + fasync = list_first_entry(&snd_fasync_list, struct snd_fasync, list); + list_del_init(&fasync->list); + spin_unlock_irq(&snd_fasync_lock); + if (fasync->on) + kill_fasync(&fasync->fasync, fasync->signal, fasync->poll); + spin_lock_irq(&snd_fasync_lock); + } + spin_unlock_irq(&snd_fasync_lock); +} + +static DECLARE_WORK(snd_fasync_work, snd_fasync_work_fn); + +int snd_fasync_helper(int fd, struct file *file, int on, + struct snd_fasync **fasyncp) +{ + struct snd_fasync *fasync = NULL; + + if (on) { + fasync = kzalloc(sizeof(*fasync), GFP_KERNEL); + if (!fasync) + return -ENOMEM; + INIT_LIST_HEAD(&fasync->list); + } + + spin_lock_irq(&snd_fasync_lock); + if (*fasyncp) { + kfree(fasync); + fasync = *fasyncp; + } else { + if (!fasync) { + spin_unlock_irq(&snd_fasync_lock); + return 0; + } + *fasyncp = fasync; + } + fasync->on = on; + spin_unlock_irq(&snd_fasync_lock); + return fasync_helper(fd, file, on, &fasync->fasync); +} +EXPORT_SYMBOL_GPL(snd_fasync_helper); + +void snd_kill_fasync(struct snd_fasync *fasync, int signal, int poll) +{ + unsigned long flags; + + if (!fasync || !fasync->on) + return; + spin_lock_irqsave(&snd_fasync_lock, flags); + fasync->signal = signal; + fasync->poll = poll; + list_move(&fasync->list, &snd_fasync_list); + schedule_work(&snd_fasync_work); + spin_unlock_irqrestore(&snd_fasync_lock, flags); +} +EXPORT_SYMBOL_GPL(snd_kill_fasync); + +void snd_fasync_free(struct snd_fasync *fasync) +{ + if (!fasync) + return; + fasync->on = 0; + flush_work(&snd_fasync_work); + kfree(fasync); +} +EXPORT_SYMBOL_GPL(snd_fasync_free); -- 2.35.1